voltmeter jumps to 16 with RPMs, CHG light flashes

[jeremy93ls]

Good idea, Captain. I bet I could swap a 280 alternator in less than 10 minutes.. i've had plenty of practice since getting my Z

Took it to the local Advance/Autozone/I forget which and it passed. The guy running the test also said the VR either works or doesn't.

I went ahead and found a cheap rebuilt Hitachi 14185 online and ordered it. I figure for $49, it wouldn't hurt to have an extra one to help with diagnostics.

[Captain Obvious]

Well that's sorta too bad that it passed. Makes it harder to find the problem.

Next thought is that the alternator is doing what is expected of it, but the fusible link connection between the alternator and the battery is shaky. I haven't studied it that closely, but it appears that the alternator will still run certain parts of the car even if that link is gone, but things like the headlights and the FI will run off the battery and not off the alternator. And if that connection is intermittent, you'll get swings on the voltmeter on the dash as the alternator is intermittently presented with the heavy load of the battery. And if that link is making connection, but not a good one, it's likely to heat up right at the connection ends.

So... You've got four fusible links in the engine compartment on the passenger front wheel well. Three of them are one color and are smaller than the fourth. My 78 FSM is blurry and it's hard to read the wire colors, but I believe the three smaller ones are brown and the fourth larger one I black?

The one I'm concerned with is the black one. With the engine running and a meter on the alternator output, wiggle that black link around a little and see what the meter does? If that fusible link doesn't make good connection the alternator won't charge the battery correctly.

If you see anything funky on the meter (heck, even if you don't), pull the link off and make sure everything looks clean and shiny? Not green and crusty. While you're in there pull all the links and make sure they're all nice and clean. Just make sure you don't mix up the colors.

[SteveJ]

I have seen an alternator pass at a parts store, yet I pushed my friend to replace it anyway. Sure enough, his charging problems disappeared.

I agree with the good Captain. Inspecting the links is a good idea.

[jeremy93ls]

I installed another rebuilt alternator and drove it for about 50 miles today with no problems at all. I hope that's all it needed.

Yes, 3 brownish and one black in the 78. I've got a spare set of Nissan fusible links in the glove box but haven't used them yet. They're so much smaller in diameter than the original links.. i suppose that wouldn't matter, though.

[Captain Obvious]

Cool. I've been continuing to think about this and I'm still thinking you need to take a close look at your fusible links. The more I think about it, the more an intermittent connection to the black link makes sense. Your old alternator tested good. You put in a new one (that's presumably good) and the problem "went away".

But my concern is that the problem was intermittent all along, right? Sometimes it was fine and sometimes it was screwy?

I'm worried that the link is currently making a good enough connection that the problem is not bad enough for you to notice, but intermittent connections are like that. Intermittent.

I guess what I'm saying is that I'm glad you got the car working, but I wouldn't be surprised if in a couple days from now you come back and say it's doing it again. Hoping not, but wouldn't be surprised!